This invention relates to a resistor and an electron tube incorporating the same. Such a resistor has a wide variety of applications. When used along with an electron gun of, for example, a color picture tube, the resistor supplies the respective electrodes with the divided levels of anode voltage. A voltage dividing resistor set forth in, for example, Japanese Patent Disclosure No. 80-14627 is of the type which is composed of an alumina ceramic insulation substrate, a resistive layer of ruthenium oxide glass resistive paste, which is printed on the insulation substrate, and an insulation layer prepared from borosilicate lead glass, which covers the resistance layer. The insulation layer contains aluminium oxide, thereby suppressing resistance variations resulting from high voltage knocking which may occur during in the manufacturing of a color picture tube.
However, a requirement of the above-mentioned type of resistor is that substantially no variation in resistance should occur while it is being operated at a high-temperature or even when the temperature of the resistor is raised by the Joule's heat. However, the conventional resistor has the drawbacks in that when used along with an electron tube, the resistor exhibits noticeable variations in resistance after it has operated for 200 to 300 hours, as represented by the broken line (curve P) of FIG. 6, and such variations in resistance are particularly noticeable in the side of a resistor which is subjected to a high potential, thereby leading to changes in the voltage-dividing ratio. In the event of such an occurrence, a noticeable change occurs in the distribution of voltage to the electrodes contained in the electron tube, with the result that the function of the electron lens and the picture quality of a color picture tube deteriorate.